Delrin piston seal

My delrin piston seal has been found wanting in the LG55! material is new to me and does seem incredibly "hard" with no "give". Possibly more suitable for the higher powered airguns? (12ft/lbs in UK). The material is certainly used in the UK in 12 ft/lb guns and of course I assume no-one now makes a 6ft/lb target springer? Anyone have any experience with delrin use for piston seals in low powered target rifles? The seal only cost me £5 so no great loss.